The present invention relates to a backup system for files in a network attached storage.
A magnetic disc storage apparatus stores data obtained by a computer. In order to protect the data from accident, disaster and fault, the computer transfers the data to a magnetic tape apparatus. Such a data protection procedure is generally called “backup”. In general backup, an operator manually designates a backup source device and a backup destination apparatus (such as a tape drive and a tape library apparatus) to initiate a backup process at a predetermined time and copy data to a backup device such as a magnetic tape.
A recent trend of interconnecting a plurality of host computers and storage devices to form a network is prevailing. This network is generally called a storage area network (SAN) in contrast with a local area network (LAN) such as Ethernet interconnecting a plurality of computers.
Computers and storage devices on SAN are interconnected by transmission paths such as copper cables and optical cables generally called Fibre Channel. The main advantage of SAN is provision of the environment that a plurality of computers can access each storage device in common. For example, data of a plurality of computers can be backed up in a single backup device because this backup device can be shared by the computers. In a system configuration having a number of computers and magnetic disc storage apparatuses, a tape library apparatus and a high speed tape apparatus are often used as a backup apparatus. In such a system, since the backup apparatus can be shared by a plurality of host computers, cost of the system configuration can be reduced.
With the advent of SAN, the number of environments which share a backup apparatus is increasing. A network attached storage (NAS) has therein a unique file system. This file system refers directly to a volume to back up data in the unit of volume, and data backup in the unit of file is impossible. For high speed on-line backup, it is necessary to connect a storage to a high speed I/O bus such as those in SAN and the like.